Hulu Plus would charge $10 a month but allow five current episodes of shows like "Glee" and "Modern Family" to be viewed free.ABC

Hulu, the free online TV hub, may not be for much longer.

The popular site is said to be planning to test a $10-a-month subscription service, dubbed Hulu Plus, as early as May 24 after coming under pressure from its big media backers.

Visitors will be able to watch up to five current episodes of shows such as Fox’s “Glee” and ABC’s “Modern Family” for free, but they would have to pay to gain access to a library of back episodes, the Los Angeles Times reported. It’s unclear whether Hulu would continue to run ads as well.

The dot-com has said it is profitable — taking in more than $100 million in ad revenue last year — but it is struggling to find a business model that satisfies users, content partners and corporate backers. Hulu is a joint venture of News Corp.’s Fox, Disney’s ABC and GE’s NBC. (News Corp. also owns The Post.)

Analysts doubt the site can make enough money from an Internet-only subscription plan. To be successful, they believe the service will have to connect to the TV through other devices, such as Web-enabled Blu-ray players, video-game consoles and set-top boxes.

That puts Hulu in a tough spot: in competition with cable and satellite companies that pay its corporate backers for the right to carry their programming. It would also encourage consumers who have been cutting a check each month to their cable company to cut the cord.

“Without that component, a subscription service is dead in the water,” said Arash Amel of the media research firm Screen Digest.

“But to do that puts the equity partners up against the [cable and satellite companies] and carries the ominous specter of ‘cord cutting’ that everyone is afraid of.”

Right now, Hulu acts as a middleman, licensing the content, selling ads against it and splitting revenue with its content providers. However, the online revenue is nowhere near what the TV networks get from advertisers.

Although Hulu executives have so far resisted the idea of a subscription plan, CEO Jason Kilar has made comments recently that suggest he is more or less resigned to the idea.

In March, Viacom’s Comedy Central pulled two of its most popular shows, “The Daily Show with Jon Stewart” and “The Colbert Report,” citing little economic upside.

Viacom, which also airs clips from those shows on its Comedy Central site, was competing against Hulu for ad dollars and was oftentimes being undercut.